The present invention relates, in general, to an improved micropin electrical connector system, which incorporates a two-part pin terminal including a pin and a formed metal body, and more particularly to a method and apparatus for fabricating the pin terminal. The pin terminal is used, for example, in conjunction with a two-piece connector system, including a plug component and a socket component, such as that described in prior U.S. Pat. No. 5,211,589, assigned to the assignee of the present application. The plug component is adapted to receive and secure corresponding pin terminals, such as those described in the present application, which terminals may be crimped onto the ends of interconnect wires to facilitate the assembly of wire harnesses, for example. The connector system provides both plug and socket terminations at the ends of such harnesses for in-line connections to corresponding terminations on other harnesses or for header connections to suitable electronic components such as microprocessor control elements, sensors and the like.
The rapid development of electronic systems for a wide range of industrial products and consumer goods has resulted in a heavy demand for improvements in the wire interconnects between electronic control components, the sensor elements connected to various parts of appliances, automobiles, and the like, and the various elements being controlled by such electronic components. These wired interconnects are often in the form of wire harnesses, wherein multiple wires are secured together to provide connections between specified locations and wherein the wires are provided with plug and socket terminations for interconnection with electronic components or other wire harnesses. A typical example of these harnesses and the corresponding plug and socket terminations is found in automotive applications, where increasing numbers of electronic sensors and control systems are being provided, requiring larger quantities of wire interconnects and increasingly complex wiring harnesses to provide the required connections to the various system elements.
The expanding use of wire harnesses and the increasing number of plug and socket terminations for such harnesses has highlighted the problems that have been encountered in prior interconnection systems, for as additional connectors are used, it becomes increasingly important to provide connectors which can be easily connected and disconnected and, even more importantly, can be automatically or manually assembled in harnesses accurately and easily so as to insure reliability while maintaining as low cost as possible. Generally, wiring harnesses utilizing multiple wires connected to the plug and socket components forming the harness terminations have been hand assembled, with individual wires being inserted into corresponding connector locations on both the plug and socket ends of the harness. The assemblers must select specific cables or wires for specific connections in the harness, and must secure them accurately and reliably to the corresponding plug and socket components. The plug and socket components must be constructed so that there is a positive lock for the individual wire terminals not only to retain the wires in place during the assembly process, but to enable the assembler to know that the wire is positively seated in its respective connector components. At the same time, the wires must be removable from the plug or the socket in case an error is made, so as to avoid the need to discard an entire harness if one wire is put in the wrong location. This requires a careful design of both the terminal at the end of the wire and the receiver in the plug or socket component of the connector system so that the wires can be easily handled without tangling and so that the terminals can be inserted into the connector components easily and accurately, while being removable in case errors are made, so as to insure proper positioning for reliable interconnection with, for example, other connector components.
As more wires have been included in harnesses and as connectors have been made smaller, the wire terminals have been forced into close proximity when inserted into connector components, not only making the assembly of a harness more difficult, but also causing significant problems in the manufacture of the connector itself. Thus, the downsizing of the connector system has imposed increasingly high standards for manufacturing tolerances, both for the connector housing portions and for the wire terminals. For example, by increasing the number of wires and often at the same time requiring smaller connectors, the spacing between the wires within the connector of necessity became smaller. The small connector dimensions created serious manufacturing problems, since the connector housings typically are molded from plastic materials, and the tools and dies used to form the connector parts are extremely complex. As the sizes and tolerances became smaller, the difficulty, and expense, of making the molds and maintaining them became excessive. In addition, the use of smaller and therefore more delicate parts made automated assembly of the harnesses very complex.
Yet the demand for smaller connectors with larger numbers of terminals continued, and the demand is still increasing for reductions in connector size as well as reductions in the cost of manufacturing connector housings and wiring harnesses.
The wire terminals utilized on the individual wires used in such harnesses typically have been shaped from sheet metal through a series of precision forming steps which shaped the terminal to form either a pin (male) or a receptacle (female), these terminals being shaped to fit into corresponding connector housing plug and socket portions, respectively, for retention by the methods described in the prior art. However, as the connectors have become miniaturized, it has been necessary to also miniaturize the wire terminals, and serious problems have been encountered in meeting the miniaturization requirements. It has been found, for example, that as pin terminals and receptacle terminals are made smaller, it becomes extremely difficult to maintain proper tolerances that will ensure reliable electrical contact when they are mated with each other or with other electrical components, or to maintain assembly forces within desired ranges. Thus, if the pin portion is too large for the receptacle portion, assembly becomes very difficult; on the other hand, if the pin is too small, then electrical contact is not reliably made. Furthermore, the precision forming steps required to make such terminals caused metal stress and fatigue which often resulted in broken terminals and resultant failure of electrical connections, and produced a seam on the mating surfaces which increased assembly forces and reduced electrical contact. The precision forming of the terminals also resulted in significant scrap metal loss and rounded corners which prevented positive locking action.
Thus, there has been a demand for reductions in the size of electrical connectors and/or an increase in the number of wires carried by such connectors. Further, there is a need for such connectors which can be accurately and reliable assembled, either manually or through the use of automatic machinery. The micropin connector system plug and socket housing connector components, which are described in the aforesaid prior U.S. Pat. No. 5,211,589, meet the need for such reduced size connectors. These components receive and secure the improved pin and receptacle wire terminals, respectively, which are described in that patent, and which are precision formed and secured to the ends of interconnect wires which may be used in the formation of wire harnesses.
The pin terminal for the micropin system of U.S. Pat. No. 5,211,589 is of hybrid construction; that is, it is not formed completely from sheet metal, but utilizes a solid wire nose, or pin end portion, which is secured to a harness interconnect wire by means of a formed metal body portion. The metal body portion is crimped onto the solid nose portion at its forward end, with the rearward end of the body portion being configured to receive the harness wire and to be connected to it, as by means of crimping. The use of a solid wire nose produces a better tolerance control on the diameter of the mating surface of the pin terminal than was possible with prior metal forming techniques used in forming the pin end. This provides better control of the mating forces required to interconnect components, provides an additional area of mating contact by eliminating an undulating surface and a seam on a mating surface of a pin terminal, and provides better control of alignment of the terminal pin within the connector for mating. Furthermore, the solid wire nose is more cost effective since its manufacture generates less scrap metal than does a formed sheet metal pin. In addition, the better heat dissipation of the solid pin enhances the current carrying capacity of the connector.
The forward, or distal, end of the metal body portion of the pin terminal extends over, and is crimped onto, the rearward portion of the solid wire nose to hold it firmly. The forward end of the metal body is shaped, as by folding back its distal end on itself, to produce a radial locking shoulder surface which extends 360 degrees around the circumference of the wire nose. This locking shoulder is positioned along the length of the pin in such a location as to engage a locking shoulder on a corresponding flexible locking finger in the connector housing when the pin terminal is inserted.
Because of the small tolerances in micropin connectors, a process and apparatus for assembling the above-described improved pin wire terminal is needed. Such a process must secure the solid wire pin to a formed metal body at a high speed in such a way as to ensure consistent, repeatable, and controlled fusing of the parts, using any one of a variety of conductive joining materials.